3,6-Dichloropicolinic acid is a crystalline solid melting at 150.degree.-152.degree. C useful as a pesticide and specifically adapted to be employed for the control of insects, mites, trash fish and microbes. The compound is also useful as a plant growth control agent. The compound, it use and method of preparation is taught in U.S. Pat. No. 3,317,549.
The 3,6-dichloropicolinic acid is taught in the above patent to be prepared by the acid hydrolysis of 3,6-dichloro-2-(trichloromethyl)pyridine. The 3,6-dichloro-2-(trichloromethyl)pyridine is mixed with either nitric, phosphoric or sulfuric acid and the mixture maintained for from 1/2 to 2 hours at 20.degree. to 140.degree. C.
While the above procedure gives high yields of the desired product, the overall process is very expensive due to the high production cost of the intermediate starting materials, thereby limiting the usefulness of the product. Processes are continually being sought employing more readily available and more economical starting material.
Collins et al, J. Chem. Soc., (c); pages 167-174 (1971) teach that halogens ortho and para to the ring nitrogen in pentachloropyridine are reactive with hydrazine hydrate. This reference further teaches the formation of tetrahalo-4-hydroxy pyridines from the action of aqueous sodium hydroxide on tetrahalo-4-hydrazinopyridines.